A power adapter is widely used as a power supplier for compact desktop PCs (personal computer), notebook PCs and personal information equipment. The power adapter is generally prepared only to supply power to the PCs and equipments. However, a performance of the power adapter is relatively low whereas the power adapter has a large volume and is heavy.
FIG. 1 illustrates a conventional compact computer system. The compact computer system includes a power adapter 110, a computer 104 and a cable 116. The cable 116 connects the power adapter 110 to the computer 104 so as to supply power to the computer 104. A cable 114 may be employed separately from the cable 116 to connect the computer 104 to a peripheral device 112. If the peripheral device 112 is a high power device, a separate power adapter may be employed to supply a necessary power to the peripheral device 112.
A variety of adapters including a peripheral circuit have been disclosed. One example is an USB (universal serial bus) hub adapter. In the USB hub adapter, a power is supplied simply to work an USB hub circuit included in the USB hub adapter. Similarly, in a network adapter, a power is supplied simply to work the network circuit. In a LAN (local area network) adapter, a power is supplied simply to work the LAN circuit. In an interface apparatus of an uninterruptible power source, a power is supplied simply to work an interface circuit. Further, the interface apparatus does not have a converting function on a frequency and a voltage of the power being supplied. Thus, those adaptors do not supply power to the computer but only to the circuit mounted on the adapters.